s. kouchakzadeh

The baffle sluice modules are structures designed for delivering rather a constant discharge within a specific rang of upstream water depth variation. They consist of three fixed vertical baffles each has a constant height and constant opening. The height of baffles increases in the downstream direction, but their openings decreased in the same direction. For the modules employed in farm irrigation canals four design methods have been proposed so far. Though the distances between the fixed baffles play an important role in the design process, no agreement among researchers was reported yet. In this research a comprehensive investigation was conducted to determine the proper distance of the baffles. The optimum distance should limit the range of discharge deviation from the design discharge and take into account the construction and installation restriction as well as economic consideration. Also the optimum distance for modules with different discharge is determined and suggested.

Weirs are the most common hydraulic structures for discharge measurement. Variety of weir types have been developed and used so far. Sharp crested circular weirs provide specific advantages and could be employed in different circumstances. However, the complex discharge relationship of these weirs limits their applications. In this study the currently available complex relationships of sharp crested circular weirs have been investigated and based on the hydraulic sensitivity concept, simple yet practical and reliable discharge evaluation relationships were proposed accordingly. It was shown that the relative sensitivity of circular weir is restricted to 1.2 to 2 which is lower than that of triangular weir, whereas it might be higher or lower than the sensitivity of rectangular weirs based on the range of non dimensional head value. The validity of the proposed relationships was examined according to the available experimental data which showed that for a very wide range of the employed data the discharge could be evaluated with a marginal error of less than 2.5%.

Manholes are commonly used in subsurface drainage networks while the hydraulic characteristics of this structure for design purposes and for determining the discharge capacity of the network have not investigated yet. In this research a prototype scale experimental setup was prepared using drainage corrugated pipes in order to determine the minor head loss coefficient of the manhole and to investigate its influence on the water surface profile. Data was gathered for a wide range of pipe longitudinal slopes and main pipe to lateral pipe discharge ratios. The data indicated that when the discharge ratio tends to unity the head loss coefficient decreases to a constant value. Accordingly، an average value was proposed for practical design purposes. The impact of applying such average value on the water surface profile directly upstream of the manhole was investigated and reported herein. The results indicated that applying such average value predicts the water surface elevation within a maximum error of ±15%. Higher errors belong to lower discharge values which are not of practical importance. Therefore، the application of proposed average head loss coefficient is recommended for design procedures.

The sensitivity analysis approach should be regarded as a new means which has recently been proposed for assessing flow of the irrigation networks. This approach uses the flow steady state equations and the physical conditions of irrigation channels to evaluate the response of the system to input perturbations. In this paper, some structural hydraulic sensitivity indicators were developed and utilized in studying the flow of an irrigation channel. For evaluating the efficiency of indicators and proposed analysis method, a real case was simulated by SOBEK model. Using the simulation results and introduced indicators, the flow regulation and distribution process within channel was studied. The results indicated a successful application of sensitivity indicators in evaluating system's potential in relation to alternative operational scenarios. With the calculation of these indicators, a comprehensive information system could be provided and applied in the analysis of the response potential of channel to structural perturbations, estimation of structure setting accuracy, and in the choice of suitable operation frequency there of.

The operation of an irrigation network is the result of a decision-making system in which three elements, i. e. the physical condition of the structures, control capacity, and hydraulic behavior of canal system, have important roles. The impact of these components is incorporated in the hydraulic sensitivity concept. For this purpose, the sensitivity of structures could be considered as the most important factor in the hydraulic characteristics of a system. The sensitivity analysis approach is one of the flow analysis methods that is used to forecast the flow behavior in several irrigation networks. Baffle Modules are one of the most suitable structures for flow regulating and delivery. In this paper, hydraulic sensitivity equations are presented for this type of structure. Also, the quantitative variations of the sensitivity index have been evaluated under operating conditions and compared with those of theoretical conditions. Then the influence of the sensitivity index variations on the performance of structures has been studied. This study was carried out on some modules of the Qazvin network. The results indicated that the hydraulic sensitivity of these off-takes varies under operating conditions. In some cases, variations were estimated to be more than 100%. The range of discharge variations was twice the predefined acceptable value (20%) in some offtakes.

Side channel spillways have a common usage in conveyance and distribution networks, high dams, water and wastewater treatment plants, and surface drainage networks. A side channel carries spatially varied flow with increasing discharge and their water surface profiles is a main feature in the design process. Usually, the bottom width of the channel is flared in the flow direction and an end sill is also installed at the downstream end to provide a control section and to generate an even water surface profile. In this study, the impact of installing an end sill on the flow characteristics in a non-prismatic side channel is presented. Six distinct longitudinal profiles were clearly observed in each run and the difference between the mid points of the maximum and the minimum profiles of each run was used to evaluate the sill effects on the water surface profile and the energy dissipation. The results indicated that the maximum and the minimum differences are, respectively, equal to critical depth and half of it generated at the channel downstream end. Also, based on an envelope of the data, a method was proposed to determine the maximum potential impact of an end sill that might have on the flow depth, which could also be considered as a guideline in the design process.

Bridge abutments are usually located in the floodplain zone of rivers where velocity and shear stress are not uniformly distributed. The influence of channel geometry and lateral momentum transfer in compound flow field on the scouring phenomenon has not been fully investigated and understood yet. The impact of lateral momentum transfer on the local scour at abutments terminating in the floodplain of a compound channel is presented in this paper. It is shown that, by accounting for lateral momentum transfer at small floodplain/main channel depth ratios (λa/H<0.3), estimates of maximum local scour depth are increased by up to 30%. Therefore, ignoring the influence of the lateral momentum transfer, in such circumstances, might result in unrealistic estimation of the scour depth. To draw a more general conclusion, more data are required to assess the influence of different parameters affecting the phenomenon in compound flow conditions.